Designers' creations don't stop at runways. An unprecedented number of fashion houses are inventing new perfumes that reflect the glamour, elegance, or sensuality of their clothes.

Charles Darwin noted that humans, unlike most mammals, engage in very little scent-driven socializing. But perhaps he would have arrived at a different conclusion had he witnessed the stampede on department stores when Chanel No. 19 launched in 1971, or had he known that women spent $1.92 billion in 2006 to communicate their taste and style by wearing scents from their favorite fashion designers. "When you buy the right designer fragrance, you immediately enter the world of that designer and what he or she stands for, in a much more personal way than a piece of apparel or an accessory," Michael Kors says. "You share a bit of their dream." Perfumer Sophia Grojsman, who has worked on fragrances for Yves Saint Laurent and Christian Lacroix, says, "It's a logical step that the designer a woman relies on to make her look a certain way will be the same one she turns to, to make her smell a certain way."

That's because these fragrances often aim to express, in some way, the overall style of the designer's clothes. To prove this point we conducted a quick survey in Times Square with two fragrances—Daisy by Marc Jacobs and the new Gucci by, yes, Gucci. Twenty women were asked to close their eyes, sniff, and guess which was which. Seventeen out of 20 got it right.

The design of a fragrance, like a runway collection, begins with a muse, a memory, or even an article of clothing. Thierry Mugler Angel sprung from the designer's childhood memories of cotton candy. "And you can smell it in the fragrance," says perfume consultant Ann Gottlieb, who was instrumental in the creation of Dior J'adore as well as Calvin Klein Obsession, Eternity, and Euphoria. A very chic aunt who was always surrounded by a cloud of tuberose inspired Michael Kors's signature scent. And for the new fragrance Versace, Donatella Versace recalled the jasmine that grew in the town in Italy where she was born, Reggio di Calabria.

Sometimes designers want to translate something less tangible—an idea, a feeling—into liquid. Giorgio Armani, for example, asked his perfumer, Thierry Wasser, to make a fragrance that smelled of diamonds (the result: Emporio Armani Diamonds). "They have no scent, yet they are irresistible, so I included rose because, like diamonds, it is a core symbol of femininity," Wasser says.

Interpreting these snapshots and ideas as a fragrance is the perfumer's crucial role. "Beyond the desire of the designer, I also look at their clothes, touch their fabrics, observe the women who wear them," Grojsman says. With these insights, perfumers can then develop the complexities of the scent. They understand that rose and peony notes seem whimsical and romantic only when paired with cassis or grass, or why it will take a dash of pepper or cumin to communicate a designer's seductive, almost animalistic fashion sensibility.

Designers, being designers, often help create the bottle and label, Gottlieb says. The bottle for Gucci by Gucci is embellished with the much-lusted-after horse-bit pendant. "I wanted something like jewelry," says Frida Giannini, creative director of Gucci. And the bottle of Prada Infusion d'Iris is embossed like a status handbag with a silver Prada logo and a cap in Miuccia Prada's signature shade of pale green. It can work the other way, too, with fashion imitating perfume. Nina Ricci L'Air du Temps was created long before Olivier Theyskens, the current Nina Ricci designer, was born. But he was so taken with the bottle that he used it as a guide for the twisted dresses and feather trim in his 2007 fall collection.

Fashion designers know that the power of suggestion is what ultimately closes the gap between their creation and a woman's pulse points. That is, after all, what leads her to pick up the bottle in the first place. "We smell with our eyes and brains before we smell with our noses," says Alan R. Hirsch, director of the Smell & Taste Treatment and Research Foundation in Chicago. Meaning, a rose might smell as sweet by any other name, but call it Gucci or Chanel, and it may just smell even sweeter.